1. Sexy Times: Now that Edward and Bella are married (and no longer dealing with the most sickening pregnancy and delivery ever put on film), and Mrs. Cullen has transformed into a vampire, the newlyweds can't help but get it on. After they're presented with their beloved stone cottage on the Cullen property, Edward and Bella have an extended sex scene that doesn't feature nudity but does feature a soft moaning, close ups of skin and even a wide shot of the couple passionately embracing naked (their arms obscure Stewart's breasts).
2. Bloody Battle: The climactic battle between the Cullens and the Volturi is considerably more vicious than the anti-climactic non-fight in the book. So be warned that there is a lot of action/violence in the film, and some of it is downright gasp-worthy. At the screening I attended, the audience actually yelled in disbelief more than once. Blood, beheadings and character deaths that are likely to make sensitive fans of the book cry again and again.
3. Relationship Themes: At the beginning of the movie, Bella is more than willing to make her father think she's dead, so he won't have to see her transformation into a glossy, gorgeous vampire (also, because she's afraid she'll want to exsanguinate him). One of the main criticisms of the books is how easy it is for Bella to leave her human life behind to join Edward and the Cullens in eternity. That's not exactly a positive message for teens, and if it weren't for Jacob, Bella would've allowed her father to grieve her death.
4. Decapitations Galore: "Breaking Dawn - Part 2" makes up for the lack of action in "Breaking Dawn - Part 1" in a huge way, and one of the most shocking visuals is the decapitation and burning of not one but several vampire characters throughout the story. Although the first three installments include a good bit of violence, the sheer number of scenes that feature a vampire killing via a severed head is really disturbing in the final "Twilight," particularly when it's a "mother" vampire who's engulfed in flames and then joined in death by her killer immortal toddler.
5. Read It Then See It: While Stephenie Meyer is no Jane Austen, if your teen is interested in reading more paranormal teen romances in young-adult literature, check out the following series that are coming to the big screen in 2013 or 2014: "Beautiful Creatures" by Kami Garcia and Margaret Stohl; "The Mortal Instruments: City of Bones" by Cassandra Clare; and "Dystopia" by Veronica Roth.